vulkan: Only render minimal region
It's faster to render once for every rectangle in the clip region than rendering the outline of the clip region. Especially because this reduces the time necessary to build up the frame data. In widget-factory (where we have 3 rectangles), this leads to a 5x speedup in the rendering time rendering alone. Snapshotting time goes from 10ms to ~1ms, which is another huge improvement.
Showing with 49 additions and 55 deletions